Gas turbine engines—as one type of a turbomachine—comprise several hot components during operation. Particularly components of a gas turbine burner are subject to hot conditions. If liquid fuel or water is provided to nozzles in a burner, this liquid fuel or water may pass through metal parts with elevated temperature before entering the respective outlet nozzles.
If the liquid fuel is exposed to hot walls, the risk for coking is severe. Coked oil on fluid pipe walls may results in clogging of the pipes or the nozzle and thus result in malfunctioning of the burner and consequently of the gas turbine.
If water is exposed to hot walls, there is a risk for boiling which can result in steam generation thus instable behaviour of the nozzle resulting also in instable combustion.
Due to these problems it is one approach to use insulated liquid passages, e.g. formed by a “tube in a tube” concept, mainly by concentric pipes in two layers with metallic separators keeping the gap. This is a quite complicated manufacturing process involving brazing, bending and welding. Alternatively or additionally large sections of the liquid passages were kept at an exterior of the burner so that a heat transfer from the body to the passage is reduced. Nevertheless the manufacturing can be quite laborious, including possibly manual assembly steps.
Patent application GB 2440547 A shows a fluid carrying arrangement in which an inner layer for carrying fluid is surrounded by an insulating layer. The arrangement may be manufactured by a solid freedom fabrication process like selective laser or electron beam sintering or melting. Insulating material may be ceramic. The insulating layer may be porous.